Aqueous zinc-ion batteries have drawn increasing attention due to the intrinsic safety, costeffectiveness and high energy density. However, parasitic reactions and non-uniform dendrite growth on the Zn anode side impede their application. Herein, a multifunctional additive, ammonium dihydrogen phosphate (NHP), is introduced to regulate uniform zinc deposition and to suppress side reactions. The results show that the NH 4 + tends to be preferably absorbed on the Zn surface to form a "shielding effect" and blocks the direct contact of water with Zn. Moreover, NH 4 + and (H 2 PO 4 ) À jointly maintain pH values of the electrode-electrolyte interface. Consequently, the NHP additive enables highly reversible Zn plating/stripping behaviors in Zn//Zn and Zn//Cu cells. Furthermore, the electrochemical performances of Zn//MnO 2 full cells and Zn//active carbon (AC) capacitors are improved. This work provides an efficient and general strategy for modifying Zn plating/stripping behaviors and suppressing side reactions in mild aqueous electrolyte.

Routine electrolyte additives are not effective enough for uniform zinc (Zn) deposition, because they are hard to proactively guide atomic-level Zn deposition. Here, based on underpotential deposition (UPD), we propose an "escort effect" of electrolyte additives for uniform Zn deposition at the atomic level. With nickel ion (Ni 2 + ) additives, we found that metallic Ni deposits preferentially and triggers the UPD of Zn on Ni. This facilitates firm nucleation and uniform growth of Zn while suppressing side reactions. Besides, Ni dissolves back into the electrolyte after Zn stripping with no influence on interfacial charge transfer resistance. Consequently, the optimized cell operates for over 900 h at 1 mA cm À 2 (more than 4 times longer than the blank one). Moreover, the universality of "escort effect" is identified by using Cr 3 + and Co 2 + additives. This work would inspire a wide range of atomic-level principles by controlling interfacial electrochemistry for various metal batteries.

Lithium-ion batteries (LIBs) have changed modern life-enabling mobile communication and electric vehicles. They are the most widespread energy storage devices but they are not totally suitable for sustainable development due to the limited lithium resources in countries often with underlying political disputes. [3][4][5] As alternative candidates, sodium-ion batteries (SIBs) have drawn increasing attention by both academic and industrial communities on account of the high abundance of sodium resources. [6,7] Of great promise are inexpensive, high-energy, long-lifespan, and fast-charging SIBs in order to improve on LIBs. [8] However, a key bottleneck in commercializing SIBs is to identify competitive cathodes with long lifespan, negligible volume change, cost-effectiveness, as well as high capacity. [9][10][11] Until now, several families of cathode materials have been developed for use such as layered oxides, [12,13] Prussian blues analogs, [14] and polyanion oxides. [15][16][17] Among these, sodium superionic conductor (NASICON)-structured Na x MeMe′(PO 4 ) 3 (Me/Me′ refers to transition metals) are capable of satisfying the above requirements in terms of high ionic conductivity (3D open frameworks), limited volume change (strong Sodium super-ionic conductor (NASICON)-structured phosphates are emerging as rising stars as cathodes for sodium-ion batteries. However, they usually suffer from a relatively low capacity due to the limited activated redox couples and low intrinsic electronic conductivity. Herein, a reduced graphene oxide supported NASICON Na 3 Cr 0.5 V 1.5 (PO 4 ) 3 cathode (VC/C-G) is designed, which displays ultrafast (up to 50 C) and ultrastable (1 000 cycles at 20 C) Na + storage properties. The VC/C-G can reach a high energy density of ≈470 W h kg −1 at 0.2 C with a specific capacity of 176 mAh g −1 (equivalent to the theoretical value); this corresponds to a three-electron transfer reaction based on fully activated V 5+ /V 4+ , V 4+ /V 3+ , V 3+ /V 2+ couples. In situ X-ray diffraction (XRD) results disclose a combination of solid-solution reaction and biphasic reaction mechanisms upon cycling. Density functional theory calculations reveal a narrow forbiddenband gap of 1.41 eV and a low Na + diffusion energy barrier of 0.194 eV. Furthermore, VC/C-G shows excellent fast-charging performance by only taking ≈11 min to reach 80% state of charge. The work provides a widely applicable strategy for realizing multi-electron cathode design for high-performance SIBs.

Using an eco-friendly PEDOT:PSS ink formula, a transparent and flexible nanopaper-based touch sensor was fabricated via inkjet-printing.

No abstract